Interconnect structures and methods of forming same

Abstract

Embodiments of the present disclosure include interconnect structures and methods of forming interconnect structures. An embodiment is a method of forming an interconnect structure, the method including forming a first post-passivation interconnect (PPI) over a first substrate, forming a second PPI over the first substrate, and forming a first conductive connector on the first PPI. The method further includes forming a second conductive connector on the second PPI, and forming a molding compound on top surfaces of the first and second PPIs and surrounding portions of the first and second connectors, a first section of molding compound being laterally between the first and second connectors, the first section of molding compound having a curved top surface.

What is claimed is: 
     
       1. A method of forming an interconnect structure, the method comprising:
 forming a first post-passivation interconnect (PPI) over a first substrate; 
 forming a second PPI over the first substrate; 
 forming a first conductive connector on the first PPI; 
 forming a second conductive connector on the second PPI; and 
 dispensing a molding compound in liquid form on top surfaces of the first and second PPIs and surrounding portions of the first and second conductive connectors; 
 forming a release compound on a pressure mold; 
 applying the pressure mold to bring the release compound in contact with the molding compound to form the molding compound around the first and second conductive connectors; 
 while the pressure mold is applied, performing a first curing process to partially cure the molding compound; 
 removing the release compound and pressure mold; and 
 after removing the release compound and pressure mold, performing a second curing process to finish curing the partially cured molding compound, the cured molding compound having a first section of molding compound being laterally between the first and second conductive connectors, the first section of molding compound having a curved top surface. 
 
     
     
       2. The method of  claim 1 , wherein after the applying the pressure mold, an apex of the first section of molding compound is from 25% to about 75% of a height of the first and second conductive connectors. 
     
     
       3. The method of  claim 1  further comprising after the forming the molding compound, performing a plasma cleaning process on the first and second conductive connectors. 
     
     
       4. The method of  claim 1 , wherein the curved top surface is a concave meniscus. 
     
     
       5. The method of  claim 4 , wherein the concave meniscus top surface has a concavity distance from about 10 μm to about 50 μm, the concavity distance being a depth of the concavity of the concave meniscus top surface. 
     
     
       6. The method of  claim 1  further comprising bonding a second substrate to the first and second conductive connectors, the second substrate not contacting any portion of the molding compound. 
     
     
       7. The method of  claim 1 , wherein the molding compound comprises an epoxy, a polyimide, polybenzoxazole, or a combination thereof. 
     
     
       8. A method of forming an interconnect structure, the method comprising:
 forming a contact pad on a top surface of a first substrate; 
 forming a first passivation layer on the top surface of the first substrate, the first passivation layer being on a portion of a top surface of the contact pad; 
 forming a second passivation layer on the first passivation layer, the second passivation layer being on a portion of the top surface of the contact pad; 
 forming a first post-passivation interconnect (PPI) contacting the top surface of the contact pad and extending along the top surface of the second passivation layer; 
 forming a first connector on the first PPI; 
 depositing a molding compound over the second passivation layer, the first PPI, and the first connector; 
 applying a pressure mold to bring a release compound in contact with the molding compound; 
 while the pressure mold is applied, performing a first curing process to partially cure the molding compound; 
 removing the release compound and pressure mold; and 
 after removing the release compound and pressure mold, performing a second curing process to finish curing the partially cured molding compound, the cured molding compound having a concave meniscus top surface, the concave meniscus top surface has a concavity distance from about 10 μm to about 50 μm, the concavity distance being a depth of the concavity of the concave meniscus top surface. 
 
     
     
       9. The method of  claim 8 , wherein the first passivation layer is silicon nitride, the second passivation layer is polyimide, and the first connector is a solder ball. 
     
     
       10. The method of  claim 8  further comprising:
 forming a second PPI extending over the first substrate; 
 forming a second connector on the second PPI, the second connector laterally adjacent the first connector; and 
 after the applying the pressure mold, the molding compound between first connector and the second connector having a concave meniscus top surface. 
 
     
     
       11. The method of  claim 8 , wherein the applying a pressure mold to the molding compound further comprises:
 forming a release compound on the molding compound; 
 bringing the pressure mold into contact with the release compound; and 
 forcing the pressure mold and the release compound in a direction towards the top surface of the first substrate, the release compound conforming to the first connector. 
 
     
     
       12. The method of  claim 11 , wherein the forcing the pressure mold and release compound further comprises applying from 250 kilonewtons to 350 kilonewtons of force to the pressure mold. 
     
     
       13. The method of  claim 11 , wherein during the forcing the pressure mold and the release compound, the pressure mold conforms to the first connector. 
     
     
       14. The method of  claim 8  further comprising bonding a second substrate to the first connector, the second substrate not contacting any portion of the molding compound. 
     
     
       15. The method of  claim 1  further comprising:
 forming a first contact pad on a top surface of the first substrate, the first PPI contacting the top surface of the first contact pad; and 
 forming a second contact pad on a top surface of the first substrate, the second PPI contacting the top surface of the second contact pad. 
 
     
     
       16. A method comprising:
 forming a contact pad over a first substrate; 
 forming a first passivation layer over the first substrate, the first passivation layer contacting a portion of a top surface of the contact pad; 
 forming a first post-passivation interconnect (PPI) contacting the top surface of the contact pad and extending along the top surface of the first passivation layer; 
 forming a first connector on the first PPI; 
 depositing a molding compound over the first passivation layer, the first PPI, and the first connector; and 
 forming a release compound on the molding compound; 
 bringing a pressure mold into contact with the release compound; 
 forcing the pressure mold and the release compound in a direction towards the top surface of the first substrate, the release compound conforming to and contacting the first connector; 
 while the release compound is contacting the first connector, performing a first curing process to partially cure the molding compound; 
 removing the pressure mold and the release compound, the partially cured molding compound having a concave meniscus top surface after the removing the pressure mold and the release compound; and 
 after removing the pressure mold and the release compound, performing a second curing process to finish curing the partially cured molding compound. 
 
     
     
       17. The method of  claim 16 , wherein the forcing the pressure mold and release compound further comprises applying from 250 kilonewtons to 350 kilonewtons of force to the pressure mold. 
     
     
       18. The method of  claim 16 , wherein during the forcing the pressure mold and the release compound, the pressure mold conforms to the first connector. 
     
     
       19. The method of  claim 16  further comprising bonding a second substrate to the first connector, the second substrate not contacting any portion of the molding compound. 
     
     
       20. The method of  claim 6  further comprising:
 injecting an underfill material between the cured molding compound and the second substrate, the underfill material surrounding and contacting portions of the first and second conductive connectors. 
 
     
     
       21. The method of  claim 8 , wherein the molding compound is a polymer.